Enumerating VHS's horizontal resolution

[pcchen]

Due to some filters inside the VHS recorder, you should get no aliasing, but a blurry image if you get over the limit frequency.

Well, there's no perfect filter. So you always have to be careful about aliasing, otherwise you may count aliasing as resolution. This happens a lot of times, when people say a picture looks "sharper" when it actually has more aliasing.

If the filter is perfect, it's even easier: the maximum frequency in the spectrum is the limit frequency.

 

[aths]

But you need a pattern generator, color filters and an analog monitor (without pixels) to be able to do that.

Because the phyical resolution of my Philips 9020 TV is much higher than the VHS resolution, I don't need a fully analog monitor without pixels.

Well, there's no perfect filter. So you always have to be careful about aliasing, otherwise you may count aliasing as resolution. This happens a lot of times, when people say a picture looks "sharper" when it actually has more aliasing.

If the filter is perfect, it's even easier: the maximum frequency in the spectrum is the limit frequency.

I never detected more aliasing in a VHS image than on the TV. (Certain structures and textures show moire on the normal TV picture.) Regarding filter quality I would like to know at what amplitude the 240 lines (320 "pixels" as of my consideration) are recorded. I.e. is it possible, to acutally record lets say 250 lines (333 "pixels") but with lower contrast only, or is 240 lines (or 244 lines, a value someone gave on the wiki's discussion page) the absolute maximum for any amplitude?

 

[LunchBox]

Is there a difference in resolution between SP and EP mode?

SP seems a lot more vibrant than EP...

 

[arjan de lumens]

Is there a difference in resolution between SP and EP mode?

SP seems a lot more vibrant than EP...

As I understand it, there is no theoretical difference in resolution between those two modes, but the EP mode runs the tape at 1/3 of the speed of SP, meaning that shortcomings of the physical storage medium (magnetic tape) will have a much greater effect on the output; this will probably reduce the effective resolution considerably, depending on the exact physical characteristics of the tape itself.

 

[aths]

Is there a difference in resolution between SP and EP mode?

SP seems a lot more vibrant than EP...

As I understand it, there is no theoretical difference in resolution between those two modes, but the EP mode runs the tape at 1/3 of the speed of SP, meaning that shortcomings of the physical storage medium (magnetic tape) will have a much greater effect on the output; this will probably reduce the effective resolution considerably, depending on the exact physical characteristics of the tape itself.

As far as I recognized, LP (half speed, in PAL regions; however the final LP tape speed is comparable to NTSC EP/SLP tape speed) delivers full resolution indeed; however the noise is much stronger while the contrast is much worser. It would be interesting how LP (or SLP) performs with an S-VHS-tape.

 

[LunchBox]

Ah I see!

thanks for clarifying!